"Channel" confusion
"Channel" confusion
- Subject: "Channel" confusion
- From: Scott Lehman <email@hidden>
- Date: Wed, 13 Jun 2001 18:52:42 -0700
- Organization: Harmony Central
Hi all,
I've been working on a program in OS X for a while now and haven't run
into any problems, but I've never understood all the channel references.
The first meaning of channel I think of is individual audio signal -
2-channel stereo, 5-channel surround, etc. This is what I understand to
be "mNumberChannels" member of the AudioBuffer structure, as well as
"mChannelsPerFrame" in the AudioStreamBasicDescription.
Then there are channels for devices, and I don't understand these yet.
A device channel can support a stream of audio with multiple channels,
right? I've tried playing around with various channel numbers and
everything seemed to work. At some point in the future, I expect I'll
run into problems, so...
So what is a "device channel"?
-One of N device channels where N is how many clients the driver can
service with a maximum of one client per channel?
-A mapping of a physical input or output port (say a card's TRS stereo
analog and S/PDIF inputs -> 2 input channels) to something multiple
clients can interface with.
-Whatever the drive writer does?
Are there Apple guidelines as to how devices and channels are supposed
to present the hardware?
For example, should the driver for a sound card with analog and digital
outs present itself as one output device? How many channels?
And if I have a PCI card with a single TOSLINK output that supports say
S/PDIF, AC-3, and ADAT, what would be the "expected" devices and
channels present? One output device with a channel for S/PDIF, one for
AC-3, and 8 for ADAT?
Thanks,
Scott